Method of producing carbonaceous molding compositions



Patented Mar. 30, 1954 METHOD OF PRODUCING GARBONACEOUS MOLDINGCOMPOSITIONS Charles Desmond Greaves and Bernard Roy Atkins, London,England, assignors to C. D. 'Patents Limited, London, EnglamL-a Britishcompany No Drawing. Application August 25,1950,

' Serial No. 181,586

Claims priority, application Great Britain August 30, 1949 '2 Claims.

This invention relates to improvements in the manufacture ofcarbonaceous moulding compositions and more particularly, but notexclusively, to the manufacture of such composition as are suitable forextrusion moulding in which a high degree of softness or plasticity isdesirable.

There have previously been proposed in United States Patentspecifications Nos. 2,461,365 and 2,493,383 methods of making mouldedproducts from finely-divided bituminous coal without a binding agent inwhich an intimate mixture of finely-divided coal having goodagglutinating properties with a swell-inhibiting agent is moulded andsubsequently fired at a controlled rate of increase in temperature to atemperature above 550 C. under non-oxidising conditions, the methodbeing so carried out that the resulting moulded product is not swollen,has a den sity greater than that of the coal used and has no cellularstructure visible to the naked eye.

The use of such methods of dry powder moulding places limitations uponthe shape of the articles that can be produced.

Again there has been proposed in specification of United States Patentapplication Serial No. 53,992 now Patent 2,640,787 and in specificationof United States Patent application Serial No. 95,890 now Patent2,637,072 a method of making from coal a carbonaceous mouldingcomposition, especially an extrusible composition, which method consistsin mixing at an elevated temperature subdivided coal and a softeningagent which exercises a solvent action upon the coal and consists ofhydrocarbon material such .as coal tar oil, anthracene oil and the like.Such a mixture may be moulded to the desired shape at a temperature atwhich the mixture will flow and the moulded shape is fired undernon-oxidising conditions at a controlled rate of temperature rise. Suchprocessesmay in certain cases be inconvenient because (1) the softeningagent may exercise an action upon the coal, the properties of which arein consequence modified, (2) the swelling tendency may be increased, and(3) the softening agent may be unpleasant to handle or may produce fumesduring the firing operation.

The main object of the present invention is to provide a method ofproducing a carbonaceous moulding composition in which no substantialmodification of the original coal is produced.

The present invention consists in a method of producing a carbonaceousmoulding composition which method comprises an intimate mixing ofsubdivided coal, water and a special lubricat- 2 ing agent comprisingone or more carboxyl-sub stituted celluloses such for example ascarboxymethyl cellulose. Sodium carboxy-methyl cellulose has proved verysuccessful.

This invention also includes a method of pro ducing a moulded carbonproduct, which method comprises the submission of the carbonaceousmoulding composition above referred to to a moulding or shapingoperation and they subsequent heating of the shaped article undernonoxidising conditions and at a rate of temperature rise controlled soas to prevent intumescence, to, a temperature of over 550 C.

The consistency of the moulding composition of the invention is governedby the quantity of water present which will not in general exceed 25-30per cent, this percentage being dependent on the degree of subdivisionof the coal. Hence during mixing care must be taken to limit loss ofwater by evaporation.

It may sometimes be desirable 'to add to the:

moulding composition a small proportion of a wetting agent. Suitablewetting agents are soaps, s'ulphated or sulphonated hydrocarbon de--rivatives or members of the non-ionogenic classof detergents. The mountof wetting agent em-- ployed varies with the circumstances but would;

generally be less than three per cent by weight. of the mixture and muston no account be suificient to exercise an oxidising or other chemicalaction upon the coal.

The amount of the special lubricating agent employed is so small thatthe amount of oxygen contained therein (in the cellulosic and carboxyl'groups) is not sufiicient to have a deleterious effect on the coal andthe effect of such oxygen is to some extent balanced by the hydrogenpresent in the alkyl groups.

Sulphur, selenium or other substances having similar dehydrogenatingproperties may be added to the mixture, but care must be taken to selectonly such substances as are non-reactive to water, and they arepreferably either finelydivided solids, or liquids which are readilymiscible with water or which are dispersed in a medium containing notmore than 30 per cent of water. The proportion of sulphur for examplemay be about 2% by weight of the coal. By the term non-reactive to wateris meant that the substances used shall not react to any substantialdegree with water under the conditions existing during the course of theprocess of preparing the moulding composition. Other finely-dividedsubstances may be added which exercise the function of further reducingthe swelling tendency of the coal or which confer special properties onthe final product. Examples of such substances arecarbon black,finely-divided graphite and china clay.

The coals most suitable for use in producing the composition of theinvention are those having from 1 3 to 30 per cent of volatile mattercalculated on the dry ash-free basis, :butpreferably coals having avolatile matter content of-between 14 and 25 percent are employed.

The particle size of the subdivided coal may be such that 90 per centpasses through a'100-mesh sieve but is conveniently such that theaverage particle size lies between 6 and 30microns.

The mixing of the coal, water and wettingagent may be suitably carriedout at a temperature of 35 C. but higher or lower temperatures may besatisfactorily employed. The mixing operation may advantageously beeffected over a periodof 2 to 3 hours.

The moulding compositions of the invention may if desired bede-aerated,e. g. in a de-aerating mill before submitting to extrusionmoulding which may-either be effected at normal room temperature or atan'elevated'temperature, for example, 50 C.

After shaping or moulding the composition by extrusion or otherwise themoulded article is dried either in the air why any other convenient andwell known means, care being exercised that the drying is uniform sothat the article'remains' free from cracks or distortion. It is foundthat, whereas immediately after extrusion the rods, tubes etc. producedthereby may require considerable care in handling, after drying they areeasily handled.

EwampZe I 700 1bs.of a mixtureconsisting of 70% of a South Walesstrongly coking coal and 30% of graphite were ground together in acolloidal mill to a state of fine subdivision. The above mixture wasplaced in a Z-blade type of mixer and to'this was added 268 lbs. of ajelly containing 94% of water, 5% sodium methylcarboxy cellulose and 1%of a-wetting agent soldunder the registered trade mark (LissapolN);these additives having been previously mixed to a smooth consistency.(Lissapol N has the formula:

where R is a benzenoid ring-and n'is a whole number of -8 or more.)Mixing then took place for a period of 2 hours during which thetemperature rose to 35 C. and the mixture developed a plasticconsistency. The resulting mixture was then formed into a cylindricalbillet by tamping in order to expel=extrapped air and the billet soproduced was extruded in the form of a tube. These tubes'were thenplaced in an oven, main-. tained at 50 C. for 24 hours, after which theywere packed in powdered coke in boxes which were then placed in anelectricfurnace, the temperature of which was then raised to 850 C. atthe rate of 2 C. per minute; the tubes were removed from the furnaceafter having been allowed to cool to approximately 200 C. undernon-oxidising conditions.

Example II 4076 grammes-of a mixture consisting of South Wales stronglycoking coal and 30% of graphite together with grammes of sodiumcarboxymethyl cellulose were placed in a mixer ofthe edge-runner typeand to this was added a solution of 15 cos. of a wetting agent soldunder the registered trade mark (Lissapol N) dissolved in 1410 grammesof water. The whole was thenwater, between 1 and 2.5 %-by weight of thecoal of sodium carboxymethyl cellulose, and a dehydrogenating agentnon-reactive to water selected from the group consisting of sulfur andselenium, said agent comprising about 2% by Weight of the coal.

2. A method of producing a carbonaceous moulding composition whichcomprises the steps of intimately mixing over-a period of two to threehours sub-divided coal of average particle size between'fi and 30microns, water, between 1% and 2.5%by weight of the coal of sodiumcarboxymethyl cellulose, less'than 3% by weight of the mixture of awater-soluble wetting agent, the water constituting between 25% and 30%of the weight of the mixture, and the temperature during mixingbeing-regulated to avoid appreciable water loss by evaporation.

CHARLES DESMOND GREAVES. BERNARD ROY ATKINS.

ReferencesCited in the file of this patent UN ITED STATES PATENTS NumberName Date 2,461,365 Bennett Feb. 8, 1949 2,552,597 Smith May 15, 1951FOREIGN PATENTS Number 7 Country Date 2,577 Great Britain 1867 329,437Great Britain May 22, 1930 OTHER REFERENCES Hercules, CMC Hercules Pwd.Co., Wilmington, Del., 1946, p. 4.

1. A METHOD OF PRODUCING A CARBONACEOUS MOULDING COMPOSITION WHICHCOMPRISES THE STEPS OF INTIMATELY MIXING FINELY SUB-DIVIDED COAL, WATER,BETWEEN 1% AND 2.5% BY WEIGHT OF THE COAL OF SODIUM CARBOXYMETHYLCELLULOSE, AND A DEHYDROGENATING AGENT NON-REACTIVE TO WATER SELECTEDFROM THE GROUP CONSISTING OF SULFUR AND SELENIUM, SAID AGENT COMPRISINGABOUT 2% BY WEIGHT-OF THE COAL.